For 6000 of these infants, the hearing loss was permanent. Further research collected by Dizziness and Balance estimates that 1 in every 1000-2000 newborns are congenitally deaf. 

But what exactly caused this in the first place? 

Per research carried out by The New England Journal of Medicine, genetic factors account for between 50% and 60% of hearing loss in children. Additionally, approximately 20% of babies born with genetic hearing loss manifested it as a comorbidity with another condition. According to the American Speech Language Hearing Association (ASHA), syndromes that may cause hearing loss include: 

  • Down syndrome
  • Usher syndrome
  • Treacher Collins syndrome
  • Crouzon syndrome
  • Alport syndrome
  • Waardenburg syndrome

Further research from the scientific journal PLOS ONE has noted that hearing loss commonly co-occurs with intellectual disabilities, cerebral palsy, autism spectrum disorder, and/or vision impairment

Other causes of congenital hearing loss include: 

  • Certain viral infections during pregnancy or shortly after birth, such as herpes simplex, rubella, or Congenital Cytomegalovirus
  • Premature births
  • Birth injuries
  • Maternal drug or alcohol use during the pregnancy
  • Maternal diabetes
  • Lack of oxygen during pregnancy
  • Exposure to catastrophic noise

To summarize the above, although there are many different potential causes of congenital hearing loss, genetics is chief among them. Genetic factors can either cause hearing loss directly or through a genetic syndrome. And that brings us to our next question—how does one determine what risk factors are present in their own family. 

To answer that, we'll first need a brief primer on genetics and DNA.

How Do Genetics Impact Hearing?

If it helps, think of genetics as a sort of blueprint for how your body operates, develops, and grows. Genetic instructions contained in DNA determine every physical characteristic of a person, from their height to the color of their eyes and hair. As irreducibly complex as DNA tends to be, it's far from perfect. 

There's a great deal that can go wrong, usually in the form of mutated genes. When a child is born with congenital deafness due to genetics, it can generally be traced to one of several genes. Arguably one of the most notable examples in recent memory is Tmc1. You may recall that last year, researchers at The Broad institute successfully edited mutated Tmc1 genes in rats to eliminate genetic deafness

GJB2 is another noteworthy gene when discussing congenital hearing loss. According to nature, a mutation in the gene responsible for coding one of the critical proteins required by the cochlea may cause up to 40% of nonsyndromic cases of genetic hearing loss

Occasionally, genetic hearing loss may be triggered by environmental factors rather than presenting as a congenital condition. Certain medications may result in ototoxicity for certain patients, for instance. 

Can You Have a Deaf Child Even if No One In Your Family Has Suffered From Hearing Loss?

One of the most important things to understand about congenital deafness is that it can run in families even if there is no documented history of hearing loss on either side. It's part of why, per The National Institute on Deafness and Other Communication Diseases, 90% of deaf children are born to hearing parents. Often, this is because each parent carries a trait which, though dormant in themselves, triggers a genetic mutation in their child. 

How is Congenital Hearing Loss Treated?

The first step to treatment is detection. Most newborns are screened for hearing loss shortly after birth. If it's determined that hearing loss is present in an infant, doctors may elect to run a gamut of tests to determine the cause. Typically, this is done via blood work—a small blood sample may be sent to the lab to screen for genetic mutations, while another sample may be tested for the presence of viral antibodies. 

Once doctors determine what caused the hearing loss, they can recommend treatment, if necessary. 

Raising a hearing-impaired child can be challenging. Parents may be tempted to have the child undergo a cochlear implant surgery in an effort to restore a child's hearing. Although this can result in the child leading a richer and more fulfilling life, pediatric cochlear implant surgeries do have a higher failure rate, according to research in PubMed.— and there's no guarantee they will restore hearing, either. 

When raising a deaf or hearing-impaired child, learning sign language is a good starting point, as communication plays a crucial role in early childhood development.

Beyond that, the best thing you can do is treat your child with kindness, love, and compassion.